Two thin, long, parallel wires, separated by a distance 'd' carry a current of 'i' A in the same direction. They will

Options

A. repel each other with a force of `((mu_(0)I ^(2))/(2 pid^(2)))`
B. attract each other with a force of `(mu_(0)i^(2))/((2pid ^(2)))`
C. rapel each other with a force of `(mu_(0)i^(2))/((2pid ))`
D. attract each other with a force of `(mu_(0)i^(2))/((2pid))`

Answer

D

Explanation

The force per unit length between two parallel wires carrying currnet `i_(1) and i_(2)` in the same direction is given by `F/l =(mu_(0))/(2pi) (i_(1)i_(2))/(d)`
(It is an attracting force because like currents attract each other.)
But `i_(1)=i_(2)`
`therefore` They will attract each other with a force `(mu_(0)i^(2))/((2pi d)).`